1. Field of the Invention
This invention relates to a fixing structure for optical connectors which fixes a conductive, shielding receptacle housing to a circuit board by means of a tapping screw.
2. Description of the Related Art
FIG. 4 shows a conventional optical connector.
The optical connector 35 is made up of a male optical plug 21 and a female receptacle 36. The optical plug 21 is inserted into a fitting chamber 37 of the receptacle 36 and locked there through its locking arm 27. The receptacle 36 has a pair of substantially cylindrical fixing portions 38 at its opposite sides and is fixed to a circuit board 39 with a pair of tapping screws (male screws) threaded into the fixing portions 38.
The optical plug 21 has a male housing 26 and, as best shown in FIG. 5, ferrules 41 (only one is shown) inside the housing which connect to optical fibers 33. The ferrule 41 is biased forwardly (in a connector-fitting direction) by a coil spring 42, so that its flange 43 is movable between a stopper 44 and a locking projection 45 inside the housing 26.
The receptacle 36 has a female housing 26xe2x80x2 of conductive synthetic resin material and, as best shown in FIG. 6, ferrule-receiving cylinders 44 inside the housing 26xe2x80x2. The fitting chamber 37 of the housing 26xe2x80x2 is defined by a vertical partition wall 13, and the receiving chambers 45 project integrally from the partition wall 13.
The receptacle-making synthetic-resin material contains, for example, carbon fibers to exhibit conductivity and shield against noise-making electric interference from outside and inside the housing 26xe2x80x2. The housing 26xe2x80x2 makes contact with a ground circuit (not shown) on the circuit board 39 through the fixing portions 38 at the opposite sides at the rear of the housing, a forwardly-located positioning pin 46 (FIG. 6).
The receiving cylinder 45 has at the rear side a large diameter portion 45a with a sleeve 14 inserted therein. The sleeve 14 consists of an inner waveguide (not shown) of glass or synthetic resin and a metal cylindrical holder. An optical element module 12 is located adjacent to the rear of the receiving cylinder 45. The sleeve 14 is in contact with the optical element module 12. The optical element module 12 connects through a lead terminal 19 to the circuit board 39, and a cover 47 presses the module from the rear toward the receiving cylinder 45.
The optical element module 12 includes a light emitting element (e.g. light emitting diode) module and a light receiving element (e.g. photodiode) module which are juxtaposed in correspondence to the two optical fibers 33 on the optical plug 21.
If the optical plug 21 is fitted in the receptacle 36 in FIG. 4, a small diameter portion 41a at the front of the ferrule 41 in FIG. 5 advances into a small-diameter portion 45b at the front of the receiving cylinder 45 in FIG. 6, so that the tip end of the ferrule small diameter portion 41a makes contact with the waveguide of the sleeve 14, and the front end of a ferrule large-diameter portion 41b abuts against the front end of the receiving cylinder 45.
Before the optical plug 21 and the receptacle 36 are fitted together, the housing 26xe2x80x2 of the receptacle 36 is preliminarily fixed through the positioning pin 46 (FIG. 6) to the circuit board 39, followed by, as shown in FIGS. 7 and 8, fully fixing same on the circuit board 39 by means of tapping screws 40 (only one is shown). The circuit board 39 is provided with insertion holes 48 (only one is shown) of diameter equal to or larger than that of the tapping screws 40, and each fixing portion 38 is provided with a prepared throughhole 49 of diameter smaller than the tapping screw diameter. The tapping screw 40 is threaded into the throughhole 49, while shaving the inner periphery of the latter.
With the conventional fixing structure for optical connectors, however, when the tapping screw 40 is threaded in as shown in FIG. 8, it shaves the inner periphery of the fixing portion 38 to produce shavings 32 which are of the same conductive resin material as the housing 26xe2x80x2 and which, when dropped on the circuit board 39, may cause a short in the wiring (not shown) on the circuit board 39. Further, where the circuit board 39 is used in a vertical position or upside down, the conductive shavings 32 tend to fall and cause an electrically adverse effect on other equipment and electric components located therebelow.
This invention has been accomplished to overcome the above drawbacks and an object of this invention is to provide a fixing structure for optical connectors in which a conductive housing of a receptacle of an optical connector is tightened to a circuit board with tapping screws (male screws) with resultant production of shavings at the fixing portion of the housing, but yet which is free of a malfunction such as a short caused by the shavings in the wiring on the circuit board.
In order to attain the object, according to this invention, there is provided a fixing structure for optical connectors which comprises: a circuit board; a receptacle having a conductive housing shieldingly connected to the circuit board, the housing having an integral fixing portion with a prepared hole formed therein; and a screw passed through the circuit board and screwed in the prepared hole of the fixing portion to fix the housing to the circuit board, wherein the fixing portion has a sealing wall which closes the prepared hole at a distal end thereof and an enclosed shaving receiver formed in the prepared hole, between the sealing wall and the screw, for retaining shavings produced when the screw is screwed in the prepared hole.
Preferably, the screw comprises a tapping screw, and the prepared hole comprises a hole without a thread.
Preferably, the screw comprises a bolt, and the prepared hole comprises a hole with a female thread.
Preferably, a length of the prepared hole is set greater than a projection length of the screw from the circuit board.
Preferably, the sealing wall of the fixing portion is flush with an outer wall of the housing.
The above and other objects, features and advantages of this invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.